Henry David Thoreau was a famed naturalist, philosopher, and author who resided in Eastern Massachusetts from 1817 to 1862. He was also a leading abolitionist and advocator of civil disobedience in defiance of an unjust state. He is perhaps best known for his views on simple living uncluttered by overdevelopment embodied in his famous book Walden; or, Life in the Woods. As a naturalist, he made records for the flowering dates of a number of common plant species. Now, 150 years later, a team of biologists from Boston University (BU) have compared those flowering records with those of today. They found that the flowering date for 43 common species had moved up by an average of seven days since the time of Thoreau.

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The researchers found that some unfortunate plants that were not able to adapt to the earlier spring have now vanished from this Earth. For example, there were 21 species of wild orchid in Concord, MA in the 1860s. Now, there are only six.

The research was conducted by Richard Primack, professor of biology at BU and is graduate student, Abe Miller-Rushing. Along with the help of independent Thoreau scholar, Brad Dean, they walked in the path of Henry David Thoreau, observing the same species.

They also located similar records by the botanist, Alfred Hosmer, who also followed in Thoreau's footsteps around the turn of the 20th century.

"Even though the world around us has changed quite a bit we were able to do roughly the same fieldwork he did," said Miller-Rushing, who is now the science coordinator for the Schoodic Education and Research Center, Acadia National Park, in Maine. "He couldn't possibly have been thinking about the things we are using his data for today."

Plants can adapt to climate change in two ways. They can either adjust their ranges, moving to higher latitudes or altitudes, or they can adjust their phenology, or timing of seasonal events such as blooming and leafing. Primack found that 43 common species had adjusted their phenology in the Concord area in response to rising temperatures. Since Thoreau's time, Concord's average temperature has risen by 4.3 degrees F.

Thoreau's records have given modern scientists a way to track the long-term trend of climate change. Usually, long-term trends consist of data from the last 30 or 50 years. For the first time, current data could be compared to data from the mid-1800s. Yet another significant contribution from the amazing life of Henry David Thoreau.